Have you observed that recently most diesel engine manufacturers prefer 24 valves cylinder head to 12 valves.
Let me tell you about an example of 24 valves engines; Cat 3406B, Cummins 855, and Detroit 92 series all these mentioned engines are 24 valves engines.
That means there must be reasons why such manufacturer switch from 12 valves to 24 valves.
Let’s consider 2 advantages of 24 valves engines.
1. Better airflow: There is no doubt that a 24 valves engine offer more better airflow than a 12 valves engine. Why? Because there are two valves for intake and two valves for exhaust. Without air engine could not run, because it is the combination of fuel and air that caused combustion in the cylinder.
Another evidence is the turbo. A turbo increases the power of the engine by allowing more air to the cylinder. In a similar way, an engine with two intakes allow more intake air than an engine with just one intake valve. Therefore four valve on a cylinder improves the engine performance.
We should not also forget the role of exhaust valves. A 24 valves engine uses 2 exhaust valves. The two exhaust valves allow the exhaust gases to exit the cylinder at the end of each cycle. So with two exhaust valve, the 24 valves engine could release as much as gases and as quick as possible.
With the help of two exhaust valves, it hasten the process of scavenging. No leftover exhaust gases is permitted in the cylinder before the new cycle begins.
However, you should remember that Detroit 92 series has 24 valves. But these 24 valves are all exhaust valves. Yet having 24 exhaust valves rather than 12 valves improve the engine efficiency because of scavenging period.
Let’s talk about another advantages of 24 valves over 12 valves. The 24 valves allows more coolant flow than the 12 valves. There are more water jackets around the cylinder head which helps the engine cooling system. With a better cooling system, the engine can travel without fear of overheating.
Although the decision is yours to make whether to buy a 12 valve or 24 valve engine, those are the advantages of 24 valves. The only cons of 24 valves I will like to mention is that it is a little bit more expensive to maintain than the 12 valves. For example, if you are to do a cylinder head overhauling, instead of replacing 12 valves you need to replace 24 valves and valve seals.
In all together, a 24 valves engine is more efficient and more powerful than a 12 valves engine